1. Field of the Invention
The present invention relates to a scanning system and method thereof, and more particularly to a hand-held scanning system and method thereof.
2. Description of the Prior Art
With the rapid development of information technology, the usage of electronic documents is very frequent and wide. Particularly, for the convenience of processing, transferring and saving a paper document, the paper document needs to be scanned and transformed to be an electronic document by a scanner. The scanner generally includes a flatbed scanner and a hand-held scanning system. However, for attaining an object of being convenient to scan, the hand-held scanning system is widely used to scan a small document or a document of not being scanned by the flatbed scanner, and can make the document content to be integrally transformed to be an image file for the convenience of processing and saving.
FIG. 1 is a block diagram of a hand-held scanning system 100 in a prior art. The hand-held scanning system 100 includes a digital encoder 102, a position detector 104, a trigger signal generator 106, an image sensing timing controller 108 and an image-processing unit 110. The digital encoder 102 includes a rotary wheel having a mask grating, a light source and an optical sensor having a comparator, thereby outputting a digital signal with two phases. The position detector 104 detects variation values of the two phases for detecting a position variation value of the hand-held scanning system 100 on a scanning document. The trigger signal generator 106 sends out a trigger signal according to the position variation value. The amount of the trigger signal is in direct ratio with that of a scanning line, but whether the amount of the scanning line is even within the range of the system movement or not, it is closely related to the scanning quality of the document. The image sensing timing controller 108 uses the trigger signal to control a contact image sensor for scanning the document. The image-processing unit 110 can process a scan image, such as saving, zooming, editing and so on.
However, when the hand-held scanning system 100 is moved suddenly fast or abruptly slow, namely the movement velocity of the hand-held scanning system 100 is non-constant, it results that the trigger signal generator 106 can not exactly generate the trigger signal according to the movement distance. In other words, the movement velocity of the hand-held scanning system 100 is varied (namely system 100 is moved at a non-constant velocity), and the trigger signal generator 106 sends out the trigger signal at an equal time interval, so the amounts of the scanning trigger signal in two equal movement ranges are not equal. As a result, the image sensor cannot sense the document in time and the scanning quality of the document is not good. In view of this, it need develop a new scanning system for solving the above problem.